For purposes of illustrating the invention, the keying system will be discussed in relation to a stacked modular connector arrangement. It is to be understood that the keying system is not limited to use in such an arrangement. It is well known in the art to use a plurality of electrical input/output modules that fit together in a stacked arrangement and are electrically connected together. It is also known that the modules may be mounted to a U-shaped metal rail that supports the device and provides electrical connection to ground. It is further known that the use of a keying arrangement is desirable to assure that the correct connector pairs are mated to one another.
U.S. Pat. No. 4,738,632 discloses one such keying arrangement for a plurality of modules mounted to base units. Each base unit includes a pair of key members that may be positioned in a desired location by inserting a tool to remove the keying member from an aperture, manually turning the key member to a desired orientation and reinserting the member in the new orientation.
Other keying systems include hermaphroditic mating members, each having an essentially one-half of a post and a corresponding recess adapted to receive the cooperating portions of the other member. One example of this type may be found in U.S. Pat. No. 4,822,305. Again, these members must be removed from respective apertures of the mating connectors and manually reinserted into the apertures.
It is desirable, however, to have a keying system that does not require either partial or full removal of a member from an aperture of a housing to change the keying orientation, thereby saving assembly time.
It is further desirable to have a keying system that provides audible and tactile assurance that the desired orientation has been reached.